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In Reply to: RE: My experiences with new M-60 Mk.3.3s, good and not-so-good posted by jeffreybehr on April 23, 2016 at 14:28:07
Sound-Coated the transformer cover, moved the pair of 1uF Platinums--that amp was humming a bit because I wasn't smart enough the first time to get both caps far enough away from the AC-filament cables--and added a pair of 0.47uf Platinums to the powersupply poles supplying Vs1*.
Will get the 0.47uFs installed and the 1uFs moved in the other amp, and then they'll cook for weeks while I fool around building another equipment rack, this time with 80/20 stuff. (Can't afford the rack/s I want.)
* JIC you haven't read Ralph's note, the former V1 is now two 'N7s with sections in parallel, labeled V1a and V1b.
Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
Bypassing have been long term best practice for us amateurs but I'm not too sure that it's a good idea after all.
Real world capacitors are capacitors with unavoidable small inductance and resistance so we should design our circuits with that in mind that they indeed are resonators at a given frequency.
By paralleling (different values) of capacitors might interact with each others like a parallel resonant circuit. Our perception of an improvement by the added capacitors might not be an improvement after all. Verifying the implementation by measuring the circuit before and after can give us a hint.
So, I believe your intention by replacing the originally 150uF capacitors is the better approach.
For my own DIY M60 I've installed 4-pole electrolytic capacitors followed by electronic chokes followed by polypropylene capacitors. No bypassing.
It does measure excellent for sure but is it really a better implementation soundwise compared to Ralphs approach? Maybe, maybe not.
Ralphs passive PSU design is guaranteed to be long stable solution without any risk for a meltdown of the output tubes nor our beloved bass drivers.
Long time lurker and first time poster in ANY forum.
I recently completed a kit build of a pair of M60's and I am loving them. It was a project that was way over my head and with Ralph's generous/patient support I got through it. I have also been bitten by the modification bug and have upgraded signal path resistor quality (same values) to great effect. My question to jeffreybehr (and anyone else who wants to add their thoughts) is; what are the sonic benefits of all of the additional capacitance (bypass capacitors)?
If this has been covered before, please forgive and point me in the right direction.
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